Solved! LG Tv 55LB7200

[Kruz0]

I have a LG tv and the screen goes black but sound stays on. Flashlight test and still has a image. I replaced for a new powerboard, I'm assuming because the power cable plugs into it, installed it and the problem happens faster now. It used to happen every half hour but now it happened in under a minute. Please advise me or someone got same problem. I like this... Is 3D TV. Thanks

 

[BEAUFORD_SAVAGE]

You probably have bad backlight LED's. This is a big job, as the entire TV needs to come apart to get to the LED strips.
There are several diffusion panels behind the actual LCD screen. These should ALL come out at the same time. If you get the order of the diffusors
wrong, The screen will end up with hotspots, or just look abnormal. Keep them all together on removal, and replacement. You will need a power supply that can reach about 3Volts X the number of LED's on a strip to test each strip. or 3Vdc times ALL the LED's per circuit, as they are in series. There are usually 2 separate banks with 1/2 the LED's on each bank. DO NOT Exceed 3 volts per LED, or you will damage all of them in one shot. If you go to far below 3 volts per LED, none of them will turn on. Leading you to possibly believe they MAY be bad when they possibly are not. Make certain to carefully remove ribbon cables and all other cables to front panel, or again you will damage the TV. I am waiting for LED Strips myself for a large TV that has some dead LED's. I have a Lab quality supply where I can limit the current, and so not worry about damaging the backlights. Without a proper power supply, you cannot test the LED strips, as the LEDS I have seen are not easily (or at all) able to be tested individually, depending on the type of strips you have. . Since you have replaced your power supply board, it is VERY likely it is the back-lights. Because these lights age, ALL led strips should be changed at once if you change any. Besides, you don't want to do this job more than once.
By the way, just to add to the fun, the LCD panel is very thin glass. Handle with extreme care.
SHEESH. I didn't mean to write a book, but this is, as I said, a big job, that can damage your TV permanently if not done right.

Good luck. Ask questions if you want.